It is reported that a surfactin has various functions such as an antibacterial activity, a hemolyzing property and an activity to inhibit a protein denaturation in addition to a high surfactant property. Therefore, a surfactin is useful as a multi-functional material. It is known that a microorganism belonging to genus Bacillus produces a surfactin, and a surfactin can be industrially produced on a large scale by culturing the Bacillus microorganism (Patent Document 1 and the like). A method for producing a surfactin and a salt thereof from a culture fluid containing the surfactin is exemplified by:
1) a method in which the culture fluid is acidified, a mixture of methylene chloride:methanol=2:1 by volume is added thereto so as to extract the surfactin in an organic layer, the obtained extract is concentrated, and then the surfactin is purified by thin layer chromatography (TLC) (Patent Document 2);2) a method in which octane is added to the culture fluid (pH 6), an organic layer is concentrated, and the surfactin is purified with ultrafiltration (Non-Patent Document 1);3) a method in which an insoluble component such as a fungus body is removed from the culture fluid by centrifugation or the like, the obtained fluid is acidified to obtain a precipitate, methylene chloride is added to the precipitate to extract the surfactin, an organic layer is concentrated, an alkaline aqueous solution is added thereto, an organic layer is discarded, an aqueous layer is acidified to obtain a precipitate, and the precipitate is freeze-dried (Patent Document 3).